Select all the true statements. A) If the input graph has edges with negative lengths, we can add a large positive number to the edge lengths to make all edge lengths positive and run Dijkstra to solve the single-source shortest path problem. B) In Dijkstra algorithm, when a vertex v is added to the known region R, its estimate distance dist(v) is correctly set to the length of the shortest path from the source vertex s to v. C) A graph is directed acyclic if and only if it has a topological order of the vertices. D) Testing whether a graph is a directed acyclic takes O(IVI+IE) time. DA B C D